1. Field of the Invention
The present invention relates to a disposable composite syringe, and, more particularly, relates to a composite syringe in which the needle can be sealed so as to prevent erroneously pricking or puncturing people who may come into contact with the syringe.
2. Description of the Prior Art
Every medical needle, once used, is usually thrown away, whether it is an ordinary needle of the injector type or a vein needle retained for intravenous drip injection of a liquid medicine or for transfusion of blood. The acute needle ends are covered with proper protectors, before being discarded, in order to prevent injury to the people who come into contact with the needles. However, those who work in various medical fields and handle the needles are still exposed to danger, because the needle ends may possibly cause injury when attaching the protectors thereto. Such an accident could cause a serious problem in addition to the simple pain due to a skin prick. For example, the needle ends which have been used on patients are sometimes polluted or exposed to various pathogens such as bacilli and viruses, thereby exposing healthy people to such bacilli and viruses.
Many ideas directed to prevention of such an erroneous exposure by the used needles include those which are disclosed in the Japanese Unexamined Utility Model Publications: Sho. 60-55448; Sho. 61-85239; Hei. 4-58256, the Unexamined Patent Publications: Hei. 4-244167; Hei. 2-1288; Hei. 4-90766; Sho. 62-144666; Sho. 63-317160; Sho. 64-86981, and the Domestic Re-Publication of Unexamined International Patent Application: Hei. 3-504808.
Publications 60-55448 and 61-85239 disclose protectors that have sockets of a modified shape. An example of the sockets has an enlarged diameter enlarged towards its end with another socket having a flange adjacent thereto, and still another socket has slits extending longitudinally thereof.
Disclosed in Publications 4-58256 and 4-244167 are some specially designed protectors. One of them has a bellows that can be stretched towards an end thereof to fully cover the injector. The other protector comprises a housing that consists of a basal portion and a compressible portion flexibly connected thereto. An acute end of the injector needle accommodated in this housing is caused to pierce the retracted compressible portion.
Disclosed in Re-Publication 3-504808, Publications 2-1288 and 4-90766 are injectors each comprising a retractable needle. Plungers engage with and retract the used needles into outer cylinders.
Further, Publications 62-144666, 63-317160 and 64-86981 disclose injectors each having a cylindrical protector fitted on an outer cylinder. This protector is slidable longitudinally of the cylinder so as to cover the whole injector.
The various prior art injectors listed and discussed above seem to be effective in preventing the needles from unintentionally pricking the user's skin. However, they still are disadvantageous for the following reasons.
The modified socket protectors must be removed from and fitted again on the used injectors. Such a re-fitting of the socket will possibly cause an accidental, erroneous pricking of the skin. Sockets of a complicated structure will increase manufacturing cost and complicate use of the injectors.
Injectors having retractable needles cannot be manufactured merely by modifying the conventional design of ordinary injectors. A sophisticated structure for injectors of this type will not only render them expensive but also difficult to use.
Injectors of the other type having the slidable protectors are easier to operate, although certain means or members for slidably holding the protectors must be added to the ordinary injectors. Such additional means or members will also increase manufacture cost.